Abstract: A magnetic field generator for producing a homogenous magnetic field region. The magnetic field generator comprises: a plurality of main magnet coils arranged in a cylindrical fashion; a plurality of shielding coils arranged in a cylindrical fashion, and located radially outward of the plurality of magnets; and wherein the main magnet coils and shielding coils are configured to shape a magnetic field which comprises at least one low fringe field region when in operation. A method for designing an MRI system that produces a low fringe field region. The method comprises: defining a solution space; defining a field of view, a center field and homogeneity requirements; defining fringe field requirements; and running an optimization algorithm to determine coil positions.

Abstract: Described herein is a method and system for shimming an MRI magnetic field generating assembly, wherein a plurality of shims are secured relative to a surface of the magnetic field generating assembly to at least partially correct inhomogeneities in the magnetic field generated by the magnetic field generating assembly. In one aspect, the shims are arranged along a plurality of concentric geometric shapes each having at least five sides. In an alternative aspect, the shims are arranged in a plurality of rows and columns, where the rows are normal to the columns. In another aspect, at least one of the shims is a flat plate of magnetic material including a top edge, a bottom edge, side edges, and face surfaces.

Abstract: A magnetic field generating device is disclosed having an arrangement of permanent magnets, each permanent magnet (PM) having a north end and a south end, and each aligned in the same north-south orientation. The PM arrangement is configured to have a surface at the north polarity end, a surface at the south polarity end, or a surface at both ends. A layer of ferromagnetic material is securely disposed at one of the surfaces of the PM arrangement, the layer having a thickness equal to or less than about 15 millimeters.

Abstract: A method of operating an imaging system having a main coil and a shield coil electromagnetically coupled to the main coil, wherein the method includes monitoring for an external environmental fluctuation of electromagnetism, and controlling current flow through the main and shield coils based upon the monitoring using a quench heater.

Abstract: A method of protecting an MR imaging system including a plurality of coil groups includes connecting at least one first diode between terminals of a first coil group, connecting at least one second diode between terminals of a second coil group, wherein the second group is connected to the first coil group via a separation line, and connecting at least one quench heater between the separation line and the first and second diodes.

Abstract: A magnetic field generator for producing a homogenous magnetic field region. The magnetic field generator comprises: a plurality of main magnet coils arranged in a cylindrical fashion; a plurality of shielding coils arranged in a cylindrical fashion, and located radially outward of the plurality of magnets; and wherein the main magnet coils and shielding coils are configured to shape a magnetic field which comprises at least one low fringe field region when in operation. A method for designing an MRI system that produces a low fringe field region. The method comprises: defining a solution space; defining a field of view, a center field and homogeneity requirements; defining fringe field requirements; and running an optimization algorithm to determine coil positions.

Abstract: A method for positioning permanent magnetic blocks includes providing a plurality of magnetized blocks, positioning the magnetized blocks on a yoke in a row by applying a mechanical force at a first end of the row with a first clamping member and at a second end of the row with a second clamping member, and repositioning the blocks by reducing the mechanical force at the first end by moving the first clamping member away from the first end, and moving the second clamping member toward the second end.

Abstract: A product line of MRI systems includes a first MRI system including a first yoke and a plurality of magnet blocks forming a first central assembly disposed on the first yoke. The product line also includes a second MRI system including a second yoke, a plurality of magnet blocks forming a second central assembly disposed on the second yoke and shaped the same as the first central assembly, and a first set of magnet blocks mounted to the second yoke at a periphery of the second central assembly.

Abstract: A method of operating an imaging system having a main coil and a shield coil electromagnetically coupled to the main coil, wherein the method includes monitoring for an external environmental fluctuation of electromagnetism, and controlling current flow through the main and shield coils based upon the monitoring using a quench heater.

Abstract: The present invention is directed to a method of shimming a magnet assembly of an MR imaging system such that a desired B0 field strength may be created with minimal inhomogeneities therethrough. With this method, sufficient shimming of the magnet assembly may be achieved without requiring mechanical variations to the magnet assembly after the magnet assembly has been assembled. The invention analyzes variations from the desired B0 field and inhomogeneities at a number of target points along the magnet assembly or B0 field. A comparison is then made at each point to determine a shimming or weighting factor such that the desired overall B0 field strength and targeted field homogeneity is achieved. Active and/or passive shim elements may then be incorporated into the magnet assembly at each target point to achieve the desired overall field strength and minimum overall field homogeneity.

Abstract: A product line of MRI systems includes a first MRI system including a first yoke and a plurality of magnet blocks forming a first central assembly disposed on the first yoke. The product line also includes a second MRI system including a second yoke, a plurality of magnet blocks forming a second central assembly disposed on the second yoke and shaped the same as the first central assembly, and a first set of magnet blocks mounted to the second yoke at a periphery of the second central assembly.

Abstract: A method for positioning permanent magnetic blocks includes providing a plurality of magnetized blocks, positioning the magnetized blocks on a yoke in a row by applying a mechanical force at a first end of the row with a first clamping member and at a second end of the row with a second clamping member, and repositioning the blocks by reducing the mechanical force at the first end by moving the first clamping member away from the first end, and moving the second clamping member toward the second end.

Abstract: The present invention is directed to a method of shimming a magnet assembly of an MR imaging system such that a desired BO field strength may be created with minimal inhomogeneities therethrough. With this method, sufficient shimming of the magnet assembly may be achieved without requiring mechanical variations to the magnet assembly after the magnet assembly has been assembled. The invention analyzes variations from the desired B0 field and inhomogeneities at a number of target points along the magnet assembly or B0 field. A comparison is then made at each point to determine a shimming or weighting factor such that the desired overall B0 field strength and targeted field homogeneity is achieved. Active and/or passive shim elements may then be incorporated into the magnet assembly at each target point to achieve the desired overall field strength and minimum overall field homogeneity.

Abstract: A superconducting magnet electrical circuit is provided for quench protection. A superconducting coil assemblage is provided including a plurality of spatially separated main and secondary magnet coil portions. The main magnet coil portions are connected in series to form at least one main coil series circuit. The secondary magnet coil portions are also connected in a series to form at least one secondary coil series circuit. At least one temperature limiting circuit is also provided. The temperature limiting circuit may be a quench heater circuit or a quench resistor circuit. The temperature limiting circuit has a plurality of quench heaters or a plurality of quench resistors connected with the superconducting coil assemblage. A superconductive switch is coupled with the superconducting coil assemblage.

Abstract: A superconducting magnet electrical circuit is provided for quench protection. A superconducting coil assemblage is provided including a plurality of spatially separated main and secondary magnet coil portions. The main magnet coil portions are connected in series to form at least one main coil series circuit. The secondary magnet coil portions are also connected in a series to form at least one secondary coil series circuit. At least one temperature limiting circuit is also provided. The temperature limiting circuit may be a quench heater circuit or a quench resistor circuit. The temperature limiting circuit has a plurality of quench heaters or a plurality of quench resistors connected with the superconducting coil assemblage. A superconductive switch is coupled with the superconducting coil assemblage.

Abstract: Described herein is a method and system for shimming an MRI magnetic field generating assembly, wherein a plurality of shims are secured relative to a surface of the magnetic field generating assembly to at least partially correct inhomogeneities in the magnetic field generated by the magnetic field generating assembly. In one aspect, the shims are arranged along a plurality of concentric geometric shapes each having at least five sides. In an alternative aspect, the shims are arranged in a plurality of rows and columns, where the rows are normal to the columns. In another aspect, at least one of the shims is a flat plate of magnetic material including a top edge, a bottom edge, side edges, and face surfaces.

Abstract: Disclosed herein is a method for assembling a magnetic field generator for a magnetic resonance imaging system. The method comprises: establishing an arrangement for a permanent magnet of a magnet assembly comprising a ferromagnetic yoke plate and a permanent magnet, wherein the arrangement includes a portion of a cavity formed from placement of a portion of a plurality of retainers attached at substantially the perimeter of the yoke plate. The method also includes populating the first portion of the cavity with a set of rails attached to the yoke plate and affixing a plurality of gliders to a plurality of magnet blocks and magnetizing the gliders and magnet blocks to form a plurality of block assemblies. Finally, the method includes sliding each block assembly of the plurality of block assemblies along a rail of the set of rails; initiating with an outermost rail and concluding with an innermost, securing each successively filled rail with a retainer.

Abstract: A superconducting magnetic resonance imaging magnet assembly is provided. The assembly includes an axial imaging bore to receive patients and a coil housing surrounding the axial bore. A main magnet coil assembly is disposed within the housing. The main magnet coil assembly includes a plurality of main magnet coils to produce a magnetic field. At least three pairs of superconductive coils are provided. In one aspect, each of the coils in at least one of the pairs comprises a superconductor wire carrying an electric current in a direction opposite to the direction of current carried by the coils of another of the superconductive pairs. The superconductor wire comprises a superconductor core and a stabilizer having a channel. The wire is wound so that the channel has a radially outward facing opening.

Abstract: A method is provided of designing a magnetic resonance imaging magnet. At least one correction coil is positioned about the axial bore of the magnet which receives patients. The correction coil is used in the design process to reduce lower order harmonics generated by the magnet. Homogeneity of the magnetic field is thereby improved at selected volumes around the magnet.

Abstract: A superconducting magnetic resonance imaging magnet assembly is provided. The assembly includes an axial imaging bore to receive patients and a coil housing surrounding the axial bore. A main magnet coil assembly is disposed within the housing. The main magnet coil assembly includes a plurality of main magnet coils to produce a magnetic field. At least three pairs of superconductive coils are provided. In one aspect, each of the coils in at least one of the pairs comprises a superconductor wire carrying an electric current in a direction opposite to the direction of current carried by the coils of another of the superconductive pairs. The superconductor wire comprises a superconductor core and a stabilizer having a channel. The wire is wound so that the channel has a radially outward facing opening.